It is well known that the abdominal musculature is difficult to isolate and strengthen. Many hours and years on exercise is generally necessary to produce a significant effect of the abdominal musculature. The prior art discloses three categories of muscular development methods and apparatuses as follows:
(1) Full range of motion; PA1 (2) Limited range of motion; PA1 (3) Compression devices.
The full range of motion devices are typified in U.S. Pat. Nos.; 4,290,597; 3,558,130; and 4,616,825. Each of these devices relates to a modification of the well known sit-up. Such inventions suffer from two major drawbacks. First, many muscle groups are indiscriminately exercised in addition to exercising of the target abdominal muscles. This results in slow development of the musculature. Second, the flexion of the lumbar and thoracic spine over a significant range of motion may exacerbate previous low back and other injuries.
Limited range of motion inventions are typified by Schleffendorf, U.S. Pat. No. 4,290,597, generally involving in an exercise called an "abdominal crunch." While such inventions may isolate the abdominal musculature, the positioning of the operator is such that maximal benefit to the operator is not achieved. Specifically in such inventions, either the legs of the operator are not extended at the knee, or the feet are not pressing against a foot stop, or the operator is leaning back, or the operator is not pulling with his arms, or the hips are not flexed, or the pelvis is not posteriorly tilted. Research performed at the direction of the inventor of the present invention has demonstrated that if any of these factors is not present, the benefit to the abdominal musculature of the "crunch" exercise will be suboptimal.